Centrifugal, as well as axial flow type, air handling blowers are widely used for circulating air in residential and commercial heating, ventilating and air conditioning (HVAC) systems. Electric motor driven centrifugal blowers or fans mounted in volute type blower housings are particularly widely used in residential HVAC systems. Substantially all HVAC blower housings are fabricated from sheet metal parts which are clamped or welded together to form the somewhat complex geometry of the blower housing.
The disadvantages of sheet metal housings are recognized, including susceptibility to corrosion, the cost of manufacturing and the hazards associated with fabricating sheet metal parts that have sharp edges and corners which can injure persons handling the blower housing as well as the final blower assembly. Moreover, sheet metal blower housings tend to amplify acoustic vibrations, become easily scratched thus removing any protective coatings and are somewhat cumbersome to insert within an HVAC unit cabinet without damaging the cabinet due to sharp edges and weight of the housing structure. Still further, recent developments in blower housing construction which require complex geometric shapes, including compound curved surfaces, also require complex and costly metal forming techniques.
Accordingly, improvements in blower housing construction for centrifugal and axial flow blowers used in HVAC systems have been desired and needed. The use of other materials in blower housing construction has been considered. Thermoplastic materials, by their nature, become hard and brittle at low temperatures and soft at high temperatures and the wide range of temperatures to which blower housings are subjected in HVAC systems is not conducive to the use of thermoplastics. Moreover, the wide range of temperatures to which HVAC system blower housings are subjected also requires, or makes highly desirable, the use of a material with a coefficient of thermal expansion similar to that of steel or similar metals, and a material which is subject to negligible creep at higher temperatures.
Accordingly, the problems associated with the development of air handling blower housings, particularly for HVAC systems, include the need to provide resistance to corrosion, negligible material creep, lack of brittleness when cold or softness when hot, a coefficient of expansion similar to steel or similar metals, chemical resistance, reduced acoustic transmissions and ease of fabricating complex housing shapes. A solution to the aforementioned problems and a desire to provide a blower housing configuration which provides an improved method of assembly have resulted in the development of the present invention.